Studies of the makeup of two newly discovered asteroids that could possibly provide the basis for future mining in space have been announced by astronomers and colleagues at NASA's Jet Propulsion Laboratory.

In work at several observatories, the astronomers have established that two near-Earth asteroids are probably composed chiefly of nickel-iron metal, much like some asteroids in the main asteroid belt and meteorites that impact the Earth.

Astronomers previously suspected that such near- Earth asteroids were extinct comets. As such, they would have probably originated in the far outer solar system where comets are believed to have formed.

Nickel-iron asteroids, on the other hand, would have probably formed in the inner solar system. Most would have originated along with objects in the main asteroid belt orbiting the Sun between Mars and Jupiter. Metallic near- Earth asteroids, however, may have began as part of the cloud of material that condensed and became the planet Earth.

One of the two asteroids studied, designated 1986 EB when it was discovered earlier this year, is known as an Aten-class asteroid -- one whose orbit is inside Earth's. The other, designated 1986 DA, belongs to the Amor class -- asteroids whose orbits are close to the Earth's, but which are beyond the Earth's orbit and do not cross it. Both are about one mile in diameter.

The observations were made by planetary astronomers Dr. Edward Tedesco of JPL and Dr. Jonathan Gradie of the University of Hawaii.

Using the 120-inch NASA Infrared Telescope at Hawaii's Mauna Kea Observatory, they found that the two asteroids have spectral qualities and albedo that put them in the same class as metallic asteroids of the main asteroid belt. Astronomers study the light, or spectra, of an object to determine its chemical composition. Albedo refers to an object's reflectivity.

Tedesco made later observations at Arizona's Kitt Peak National Observatory with Dr. Robert Nelson of JPL, and at Mauna Kea with Dr. Marc Buie of the University of Hawaii.

The astronomers noted that metallic asteroids near Earth might provide suitable sites for future mining operations in space, as has been proposed to provide raw materials for possible interplanetary expeditions in the 21st century.